class Solution {
public:

//迭代
    double myPow(double x, int n) {
      double res =1.0;
      long b = n;
      if(b<0){
          x = 1/x;
          b = -b;
      }
      while (b>0)
      {
          if(b&1)res*=x;
          x *=x;
          b=b>>1;
      }
      return res;
      

    }
};